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https://github.com/ninenines/cowboy.git
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Fix and optimize sending of WINDOW_UPDATE frames
For long-running connections it was possible for the connection window to become larger than allowed by the protocol because the window increases claimed by stream handlers were never reclaimed even if no data was consumed. The new code applies heuristics to fix this and reduce the number of WINDOW_UPDATE frames that are sent. It includes six new options to control that behavior: margin, max and threshold for both the connection and stream windows. The margin is some extra space added on top of the requested read size. The max is the maximum window size at any given time. The threshold is a minimum window size that must be reached before we even consider sending more WINDOW_UPDATE frames. We also avoid sending WINDOW_UPDATE frames when there is already enough space in the window, or when the read size is 0.
This commit is contained in:
Loïc Hoguin
parent
aedf6379cc
commit
eb4735ef7a
2 changed files with 84 additions and 36 deletions
2
Makefile
2
Makefile
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@ -15,7 +15,7 @@ CT_OPTS += -ct_hooks cowboy_ct_hook [] # -boot start_sasl
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LOCAL_DEPS = crypto
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DEPS = cowlib ranch
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dep_cowlib = git https://github.com/ninenines/cowlib 2.7.3
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dep_cowlib = git https://github.com/ninenines/cowlib better-window-updates
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dep_ranch = git https://github.com/ninenines/ranch 1.7.1
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DOC_DEPS = asciideck
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@ -30,6 +30,8 @@
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compress_buffering => boolean(),
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compress_threshold => non_neg_integer(),
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connection_type => worker | supervisor,
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connection_window_margin_size => 0..16#7fffffff,
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connection_window_update_threshold => 0..16#7fffffff,
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enable_connect_protocol => boolean(),
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env => cowboy_middleware:env(),
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idle_timeout => timeout(),
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@ -38,10 +40,12 @@
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initial_stream_window_size => 0..16#7fffffff,
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logger => module(),
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max_concurrent_streams => non_neg_integer() | infinity,
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max_connection_window_size => 0..16#7fffffff,
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max_decode_table_size => non_neg_integer(),
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max_encode_table_size => non_neg_integer(),
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max_frame_size_received => 16384..16777215,
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max_frame_size_sent => 16384..16777215 | infinity,
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max_stream_window_size => 0..16#7fffffff,
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metrics_callback => cowboy_metrics_h:metrics_callback(),
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middlewares => [module()],
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preface_timeout => timeout(),
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@ -50,6 +54,8 @@
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settings_timeout => timeout(),
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shutdown_timeout => timeout(),
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stream_handlers => [module()],
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stream_window_margin_size => 0..16#7fffffff,
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stream_window_update_threshold => 0..16#7fffffff,
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tracer_callback => cowboy_tracer_h:tracer_callback(),
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tracer_match_specs => cowboy_tracer_h:tracer_match_specs(),
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%% Open ended because configured stream handlers might add options.
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@ -57,6 +63,17 @@
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}.
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-export_type([opts/0]).
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-record(stream, {
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%% Whether the stream is currently stopping.
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status = running :: running | stopping,
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%% Flow requested for this stream.
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flow = 0 :: non_neg_integer(),
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%% Stream state.
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state :: {module, any()}
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}).
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-record(state, {
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parent = undefined :: pid(),
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ref :: ranch:ref(),
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@ -81,9 +98,12 @@
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http2_status :: sequence | settings | upgrade | connected | closing,
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http2_machine :: cow_http2_machine:http2_machine(),
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%% Flow requested for all streams.
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flow = 0 :: non_neg_integer(),
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%% Currently active HTTP/2 streams. Streams may be initiated either
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%% by the client or by the server through PUSH_PROMISE frames.
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streams = #{} :: #{cow_http2:streamid() => {running | stopping, {module, any()}}},
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streams = #{} :: #{cow_http2:streamid() => #stream{}},
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%% Streams can spawn zero or more children which are then managed
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%% by this module if operating as a supervisor.
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@ -259,8 +279,8 @@ frame(State=#state{http2_machine=HTTP2Machine0}, Frame) ->
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maybe_ack(State#state{http2_machine=HTTP2Machine}, Frame);
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{ok, {data, StreamID, IsFin, Data}, HTTP2Machine} ->
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data_frame(State#state{http2_machine=HTTP2Machine}, StreamID, IsFin, Data);
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{ok, {lingering_data, _StreamID, DataLen}, HTTP2Machine} ->
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lingering_data_frame(State#state{http2_machine=HTTP2Machine}, DataLen);
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{ok, {lingering_data, StreamID, DataLen}, HTTP2Machine} ->
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lingering_data_frame(State#state{http2_machine=HTTP2Machine}, StreamID, DataLen);
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{ok, {headers, StreamID, IsFin, Headers, PseudoHeaders, BodyLen}, HTTP2Machine} ->
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headers_frame(State#state{http2_machine=HTTP2Machine},
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StreamID, IsFin, Headers, PseudoHeaders, BodyLen);
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@ -292,30 +312,38 @@ maybe_ack(State=#state{socket=Socket, transport=Transport}, Frame) ->
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end,
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State.
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data_frame(State=#state{opts=Opts, streams=Streams}, StreamID, IsFin, Data) ->
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data_frame(State0=#state{opts=Opts, flow=Flow, streams=Streams}, StreamID, IsFin, Data) ->
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case Streams of
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#{StreamID := {running, StreamState0}} ->
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#{StreamID := Stream=#stream{status=running, flow=StreamFlow, state=StreamState0}} ->
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try cowboy_stream:data(StreamID, IsFin, Data, StreamState0) of
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{Commands, StreamState} ->
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commands(State#state{streams=Streams#{StreamID => {running, StreamState}}},
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StreamID, Commands)
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%% Remove the amount of data received from the flow.
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%% We may receive more data than we requested. We ensure
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%% that the flow value doesn't go lower than 0.
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Size = byte_size(Data),
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State = update_window(State0#state{flow=max(0, Flow - Size),
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streams=Streams#{StreamID => Stream#stream{
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flow=max(0, StreamFlow - Size), state=StreamState}}},
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StreamID),
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commands(State, StreamID, Commands)
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catch Class:Exception ->
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cowboy:log(cowboy_stream:make_error_log(data,
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[StreamID, IsFin, Data, StreamState0],
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Class, Exception, erlang:get_stacktrace()), Opts),
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reset_stream(State, StreamID, {internal_error, {Class, Exception},
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reset_stream(State0, StreamID, {internal_error, {Class, Exception},
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'Unhandled exception in cowboy_stream:data/4.'})
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end;
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%% We ignore DATA frames for streams that are stopping.
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#{} ->
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State
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State0
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end.
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lingering_data_frame(State=#state{socket=Socket, transport=Transport,
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http2_machine=HTTP2Machine0}, DataLen) ->
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Transport:send(Socket, cow_http2:window_update(DataLen)),
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HTTP2Machine1 = cow_http2_machine:update_window(DataLen, HTTP2Machine0),
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State#state{http2_machine=HTTP2Machine1}.
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lingering_data_frame(State, _StreamID, _DataLen) ->
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%% We do nothing when receiving a lingering DATA frame.
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%% We already removed the stream flow from the connection
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%% flow and are therefore already accounting for the window
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%% being reduced by these frames.
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State.
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headers_frame(State, StreamID, IsFin, Headers,
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PseudoHeaders=#{method := <<"CONNECT">>}, _)
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@ -410,7 +438,7 @@ headers_frame(State=#state{opts=Opts, streams=Streams}, StreamID, Req) ->
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try cowboy_stream:init(StreamID, Req, Opts) of
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{Commands, StreamState} ->
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commands(State#state{
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streams=Streams#{StreamID => {running, StreamState}}},
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streams=Streams#{StreamID => #stream{state=StreamState}}},
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StreamID, Commands)
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catch Class:Exception ->
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cowboy:log(cowboy_stream:make_error_log(init,
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@ -449,7 +477,7 @@ early_error(State0=#state{ref=Ref, opts=Opts, peer=Peer},
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rst_stream_frame(State=#state{streams=Streams0, children=Children0}, StreamID, Reason) ->
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case maps:take(StreamID, Streams0) of
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{{_, StreamState}, Streams} ->
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{#stream{state=StreamState}, Streams} ->
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terminate_stream_handler(State, StreamID, Reason, StreamState),
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Children = cowboy_children:shutdown(Children0, StreamID),
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State#state{streams=Streams, children=Children};
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@ -494,10 +522,10 @@ down(State=#state{opts=Opts, children=Children0}, Pid, Msg) ->
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info(State=#state{opts=Opts, streams=Streams}, StreamID, Msg) ->
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case Streams of
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#{StreamID := {IsRunning, StreamState0}} ->
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#{StreamID := Stream=#stream{state=StreamState0}} ->
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try cowboy_stream:info(StreamID, Msg, StreamState0) of
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{Commands, StreamState} ->
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commands(State#state{streams=Streams#{StreamID => {IsRunning, StreamState}}},
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commands(State#state{streams=Streams#{StreamID => Stream#stream{state=StreamState}}},
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StreamID, Commands)
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catch Class:Exception ->
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cowboy:log(cowboy_stream:make_error_log(info,
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@ -586,15 +614,13 @@ commands(State0=#state{socket=Socket, transport=Transport, http2_machine=HTTP2Ma
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State0
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end,
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commands(State, StreamID, Tail);
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commands(State=#state{socket=Socket, transport=Transport, http2_machine=HTTP2Machine0},
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StreamID, [{flow, Size}|Tail]) ->
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Transport:send(Socket, [
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cow_http2:window_update(Size),
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cow_http2:window_update(StreamID, Size)
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]),
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HTTP2Machine1 = cow_http2_machine:update_window(Size, HTTP2Machine0),
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HTTP2Machine = cow_http2_machine:update_window(StreamID, Size, HTTP2Machine1),
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commands(State#state{http2_machine=HTTP2Machine}, StreamID, Tail);
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%% Read the request body.
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commands(State0=#state{flow=Flow, streams=Streams}, StreamID, [{flow, Size}|Tail]) ->
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#{StreamID := Stream=#stream{flow=StreamFlow}} = Streams,
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State = update_window(State0#state{flow=Flow + Size,
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streams=Streams#{StreamID => Stream#stream{flow=StreamFlow + Size}}},
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StreamID),
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commands(State, StreamID, Tail);
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%% Supervise a child process.
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commands(State=#state{children=Children}, StreamID, [{spawn, Pid, Shutdown}|Tail]) ->
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commands(State#state{children=cowboy_children:up(Children, Pid, StreamID, Shutdown)},
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@ -628,6 +654,25 @@ commands(State=#state{opts=Opts}, StreamID, [Log={log, _, _, _}|Tail]) ->
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cowboy:log(Log, Opts),
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commands(State, StreamID, Tail).
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%% Tentatively update the window after the flow was updated.
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update_window(State=#state{socket=Socket, transport=Transport,
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http2_machine=HTTP2Machine0, flow=Flow, streams=Streams}, StreamID) ->
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#{StreamID := #stream{flow=StreamFlow}} = Streams,
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{Data1, HTTP2Machine2} = case cow_http2_machine:ensure_window(Flow, HTTP2Machine0) of
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ok -> {<<>>, HTTP2Machine0};
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{ok, Increment1, HTTP2Machine1} -> {cow_http2:window_update(Increment1), HTTP2Machine1}
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end,
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{Data2, HTTP2Machine} = case cow_http2_machine:ensure_window(StreamID, StreamFlow, HTTP2Machine2) of
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ok -> {<<>>, HTTP2Machine2};
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{ok, Increment2, HTTP2Machine3} -> {cow_http2:window_update(StreamID, Increment2), HTTP2Machine3}
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end,
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case {Data1, Data2} of
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{<<>>, <<>>} -> ok;
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_ -> Transport:send(Socket, [Data1, Data2])
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end,
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State#state{http2_machine=HTTP2Machine}.
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%% Send the response, trailers or data.
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send_response(State0, StreamID, StatusCode, Headers, Body) ->
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@ -741,7 +786,7 @@ goaway(State, {goaway, _, Reason, _}) ->
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%% Cancel client-initiated streams that are above LastStreamID.
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goaway_streams(_, [], _, _, Acc) ->
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Acc;
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goaway_streams(State, [{StreamID, {_, StreamState}}|Tail], LastStreamID, Reason, Acc)
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goaway_streams(State, [{StreamID, #stream{state=StreamState}}|Tail], LastStreamID, Reason, Acc)
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when StreamID > LastStreamID, (StreamID rem 2) =:= 0 ->
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terminate_stream_handler(State, StreamID, Reason, StreamState),
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goaway_streams(State, Tail, LastStreamID, Reason, Acc);
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@ -780,7 +825,7 @@ terminate_reason({internal_error, _, _}) -> internal_error.
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terminate_all_streams(_, [], _) ->
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ok;
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terminate_all_streams(State, [{StreamID, {_, StreamState}}|Tail], Reason) ->
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terminate_all_streams(State, [{StreamID, #stream{state=StreamState}}|Tail], Reason) ->
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terminate_stream_handler(State, StreamID, Reason, StreamState),
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terminate_all_streams(State, Tail, Reason).
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@ -820,13 +865,13 @@ stop_stream(State=#state{http2_machine=HTTP2Machine}, StreamID) ->
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end.
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stopping(State=#state{streams=Streams}, StreamID) ->
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#{StreamID := {_, StreamState}} = Streams,
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State#state{streams=Streams#{StreamID => {stopping, StreamState}}}.
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#{StreamID := Stream} = Streams,
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State#state{streams=Streams#{StreamID => Stream#stream{status=stopping}}}.
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%% If we finished sending data and the stream is stopping, terminate it.
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maybe_terminate_stream(State=#state{streams=Streams}, StreamID, fin) ->
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case Streams of
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#{StreamID := {stopping, _}} ->
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#{StreamID := #stream{status=stopping}} ->
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terminate_stream(State, StreamID);
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_ ->
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State
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@ -849,12 +894,15 @@ terminate_stream(State0=#state{socket=Socket, transport=Transport,
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end,
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terminate_stream(State, StreamID, normal).
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terminate_stream(State=#state{streams=Streams0, children=Children0}, StreamID, Reason) ->
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%% We remove the stream flow from the connection flow. Any further
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%% data received for this stream is therefore fully contained within
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%% the extra window we allocated for this stream.
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terminate_stream(State=#state{flow=Flow, streams=Streams0, children=Children0}, StreamID, Reason) ->
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case maps:take(StreamID, Streams0) of
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{{_, StreamState}, Streams} ->
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{#stream{flow=StreamFlow, state=StreamState}, Streams} ->
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terminate_stream_handler(State, StreamID, Reason, StreamState),
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Children = cowboy_children:shutdown(Children0, StreamID),
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State#state{streams=Streams, children=Children};
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State#state{flow=Flow - StreamFlow, streams=Streams, children=Children};
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error ->
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State
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end.
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